After playing with the Keysight N9322C for a few days I have garnered sufficient skill to make this full featured instrument reveal just a fraction of its capability. A far more involved exploration will be posted in the Road Test review section, but for now, here is a quick illustration of just one very cool feature.
The TI CC11XL development kit comes with two TRXEB boards and several radio modules. The pre-loaded firmware includes a mode that allows one board to send out a continuous stream of packets which can then be received by the second board. I set this test up and without much surprise, observed it working by viewing the increasing packet counters on both the transmitter and receiver. With a new spectrum analyzer available, I thought it would be instructive to see if I could use the FSK demodulation feature to see the packet data.
A handy adjustable wide band antenna is included with the Keysight N9322C as well as a pair of BNC to N adapters. Without too much difficulty and only a handful of references to the user guide, the N9322C was configured to demodulate FSK signals emanating from the TRXEB. Most of my electronics work occurs in the time domain, so configuring an oscilloscope is mostly a matter of using hard wired muscle memory and instinct. Perhaps it is this time domain dominance that slowed me down, as it took me awhile to configure the N9322C to do what I knew it could do and what I wanted it to do. Some of the time was spent trying to figure out the menu system, decipher awkward language in the user manual and perform on the fly corrections to outdated text in the user guide. Eventually the N9322C was properly configured. The video below explains the test set up and shows a little of how the N9322C represents decoded FSK packets next to an illustration of how the Tektronix MDO4104-3 represents the same packets.
The representations are quite different. Both representations are useful in my mind and appropriate for different purposes. Together these instruments provide a pretty complete understanding of what is happening inside an FSK packet transmission.
A benefit of using sophisticated capabilities in instruments like these is that it allows the user to see things that in the past were either restricted to the imagination or left hidden under a cloak of magic, never to be really understood. After seeing the waveforms produced by these two instruments and not quite understanding them, I looked up information on GMSK (Gaussian Minimum Shift Keying) modulation on Google. I have to say, there is a lot of fine information available on the web that can be very instructive.
At any rate, watch the video below to see how the TI CC11XL can easily be configured to burst out sub-GHz packets and to see how two modern analytical instruments can snatch those packets out the air and turn them into very informative representations for consumption by technically inclined individuals.
Here is a screen capture from the Tektronix MDO4104-3 that shows some of the set up and measurement details.
To get a better sense of the various ways the N9322C can represent demodulated FSK data take a look at the video below. This short video was made using a feature available in the free Keysight HSA and BSA PC software. This remote control software allows total control of the N9322C and provides a near real time view of the spectrum analyzer screen on your PC. One of the features allows an AVI movie file to be generated from the PC version of the instrument screen. Great for documenting tests and sharing them with your team, or Element 14 community members.
In the video you will see the eye diagram of the FSK signal followed by an RF triggered deviation waveform then a binary decoded listing of the 88 symbols (11 bytes) that I think make up a single packet. If you look carefully at the waveform you will notice the last several symbols are changing periodically while most of the symbols at the front end are steady. Look carefully also at the last byte of binary data in the symbol table. The data in the last byte is incrementing with each update. My guess is that number is related to the packet count number displayed on the TI development kits.
Right there is an example of how the N9322C helped me understand the nature of a signal. Before I set up the spectrum analyzer to examine the packets I really had no idea what was in them. I determined the carrier frequency and the symbol rate through reference to the documentation, but the count data was discovered with the N9322C. Converting unsee-able radio waves into meaningful information is a very useful capability. This is just one of many capabilities in the Keysight N9322C.
Mark
